Our long-term objective is to identify the molecular factors responsible for light scattering and opacification of the lens. Light scattering can be produced in the lens by the formation of protein aggregates, the condensation of proteins into coexisting protein-rich and protein-poor liquid phases and the condensation of proteins into crystalline solid phases. In previous years, we have identified various molecular mechanisms that produce such condensates, and thereby result in light scattering and opacification in gamma crystallin solutions in vitro. Some of these mechanisms are now known to be responsible for several human genetic cataracts. We now wish to extend our work by conducting investigations of the condensates formed by the beta crystallins. Moreover, with the extensive knowledge base of gamma crystallins, we also want to explore the thermodynamic and kinetic behavior of the mixtures of beta and gamma crystallins, in an effort to emulate more realistically the situation present in the lens cytoplasm. To achieve these objectives, we propose the following Specific Aims: 1. To determine the phase diagrams, and the kinetics of aggregation of aqueous solutions of recombinant human beta crystallins, and their naturally occurring mutant and truncated forms. 2. To explore the interactions between beta and gamma crystallins, by studying the phase-diagrams and kinetics of aggregation of solutions of beta and gamma crystallin mixtures. 3. To develop a theoretical description which can predict the phase diagrams, and the kinetics of aggregation for solutions of pure beta and gamma crystallins as well as their mixtures.